In vitro fermentation patterns of rice bran components by human gut microbiota

Authors: PHAM, TUNG - University Of Arkansas; SAVARY, BRETT - Arkansas State University; Chen, Ming Hsuan; LEE, SUN-OK - University Of Arkansas; McClung, Anna

Submitted to: Nutrients
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2017
Publication Date: 11/12/2017
Citation: Pham, T., Savary, B., Chen, M., Lee, S., Mcclung, A.M. 2017. In vitro fermentation patterns of rice bran components by human gut microbiota. Nutrients. 9(11):1237. https://doi.org:10.3390/nu9111237.
DOI: https://doi.org/10.3390/nu9111237

Interpretive Summary: Whole grain rice bran is a rich source of bioactive components that have potential to promote gastrointestinal health. Among these components, feruloylated arabinoxylan oligosaccharides (FAXO), a soluble portion of non-digestible fiber after enzymatic hydrolysis, and red pigmented rice bran polyphenols (RBPP) were investigated for their prebiotic potential and the impact on human gut microbiota in vitro. Each fresh fecal samples collected from healthy adults (n = 10, 5M, 5F) with no signs or symptoms of bowel diseases or conditions received 5 treatments separately: CTRL (no substrates), FOS (fructooligosaccharides), FAXO, RBPP, and MIX (FAXO with RBPP). The treatments were incubated at 37°C in an anaerobic chamber for a 24h-period and sampled 5 times during this period. Results showed that treatment with FAXO significantly increased the production of short chain fatty acids, the fermentation products of the colonic bacteria that are beneficial to the gut health, and was comparable to those of treatment with FOS, which is a well-established prebiotic. FAXO and RBPP had synergistic effects on increasing the abundance of bacteria that generate butyrate short chain fatty acid, a fatty acid with protective effects of colon cells against cancer. Results from this study suggested that FAXO from rice bran can potentially promote colon health through a prebiotic function.

Technical Abstract: Whole grain rice is a rich source of fiber, nutrients, and phytochemicals that may promote gastrointestinal health, but such beneficial components are typically removed with the bran during polishing. Soluble feruloylated arabinoxylan oligosaccharides (FAXO) and polyphenolics (RBPP) isolated from rice bran are hypothesized to have positive impacts on human gut microbiota through a prebiotic function. Using an in vitro human fecal fermentation bioassay, FAXO and RBPP treatments were assessed for short-chain fatty acids (SCFA) production patterns and by evaluating their impacts on the phylogentic composition of human gut microbiota by 16S rRNA gene sequencing. Fresh fecal samples collected from healthy adults (n = 10, 5M, 5F) were diluted with anaerobic medium. Each sample received 5 treatments: CTRL (no substrates), FOS (fructooligosaccharides), FAXO, RBPP, and MIX (FAXO with RBPP). Samples were incubated at 37°C and an aliquot was withdrawn from each treatment tube at 0, 4, 8, 12, and 24 hours. Results showed that SCFA production was significantly increased with FAXO and was comparable to fermentation with FOS, a well-established prebiotic. RBPP did not increase SCFA productions, and no significant differences in total SCFA production were observed between FAXO and MIX indicating RBPP does not modify FAXO fermentation. Changes in microbiota population were found in FAXO treatment, especially in Bacteroides, Prevotella, and Dorea populations, indicating that FAXO might modulate microbiota profiles. RBPP and MIX increased Faecalibacterium, specifically F. prausnitzii. Combined FAXO and RBPP fermentation increased abundance of butyrogenic bacteria, Coprococcus and Roseburia, suggesting some synergistic activity. Results from this study support the potential for FAXO and RBPP from rice bran to promote colon health through a prebiotic function.